A surface emitting semiconductor laser has been researched and developed for a light source which is possible to be small in size and two-dimensionally integrated by domestic and foreign research institutes. One of problems to be solved in the surface emitting semiconductor laser is to stabilize the polarization direction of an output light. In a surface emitting semiconductor laser having an isotropic configuration, the difference of properties on two axes orthogonal to each other is not observed, so that output lights are polarized on the two axes by the same provability. This means that the polarization is not fixed in one direction. If the polarization is not stabilized in one direction, optical devices such as a polarization beam splitter having polarization dependency can not be used in optical systems such as an optical interconnection system, an optical switching system, an optical information processing system, etc.
In order to overcome such a problem, a conventional surface emitting semiconductor laser comprising an Al.sub.0.3 Ga.sub.0.7 As layer, a GaAs active layer and an Al.sub.0.3 Ga.sub.0.7 As layer successively grown on a GaAs substrate having an elliptical light emission aperture has been proposed as described in No. 3 in the Extended Abstracts (the 39th Spring Meeting, 1992), the Japan Society of Applied Physics and Related Societies".
In fabrication of the surface emitting semiconductor laser, the GaAs substrate having a thickness of, for instance, 100 .mu.m is etched to be provided with the elliptical light emission aperture.
In accordance with the provision of the elliptical light emission aperture, stress is applied to the GaAs active layer, such that the tensile stress is smaller in the long axis direction for the elliptical light emission aperture. Consequently, an output light is stabilized in polarization to be positioned on the long axis.
In the conventional surface emitting semiconductor laser, however, there is disadvantage in that the fabrication thereof is difficult, and the reliability thereof is low, because the etched light emission aperture is required to stop in the Al.sub.0.3 Ga.sub.0.7 As layer immediately below the GaAs active layer, and the Al.sub.0.3 Ga.sub.0.7 As layer is occasionally made thin.